Two school teachers who retired before 30 with $1 million share their best advice for anyone who wants to do the same

(Cultivating a sense of gratitude for everything they had helped the Olsons live frugally without feeling deprived.Joe and Ali Olson) Joe and Ali Olson spend their days traveling around the world with their one-year-old daughter, Annabelle.

Each in their early 30s, the couple were able to quit their jobs as public school teachers in August 2015 and retire after just eight years in the workforce.

By living frugally and finding a good side hustle — in their case, real estate — the couple was able to achieve financial independance relatively quickly. After purchasing their Las Vegas home at a steep discount in 2007, they started scooping up rental properties for cheap, a result of the battered housing prices during the financial crisis. They lost money at first, but eventually the market flipped and they began to turn a profit.

But even as their net worth rose, they didn't succumb to lifestyle inflation. The pair continued to save 75% of their income and resided in their 400-square-foot home.

Fifteen properties later, they were able to retire as millionaires and tackle new dreams: traveling the world and starting a family. (You can follow along with their travels on their blog, Adventuring Along.)

Impressive, yes. But they believe that financial independence and early retirement can be a reality for anyone.

And on a recent episode of the Mad Fientist's Financial Independence Podcast, they shared their best advice for anyone looking to do just that. Their secret? Shift your mindset and learn to be happy with what you have.

Joe shared a quote from philosopher John Stuart Mill that stated: "I have learned to seek my happiness by limiting my desires, rather than in attempting to satisfy them."

"For me, financial independence was really easy to get because we were happy just living in our fairly small place, and eating at home, and just being efficient with how we spent money," Joe explained to the Mad Fientist. "And so our high savings rate was just because we enjoyed simplicity. And we didn't have to cut our budget. We didn't have to deprive ourselves."

By choosing to live simply and enjoy life instead of always looking toward the next fill-in-the-blank thing that might satisfy them, Joe and Ali were able to live on around $20,000 a year without feeling like they were sacrificing full lives.

They did make sacrifices: living in a small apartment, sharing one car when they could afford two, forgoing restaurant meals. But it never felt like they were forfeiting something they truly wanted.

"We cultivated a concept of gratitude about everything," Ali says. "And once you're grateful for everything you have, to try to get more seems silly."